One of the most commonly raised arguments against communism is the question of the so-called human nature. Like all things in nature, human thought and society are in a constant state of change. The comparison may be too dull but think of pop-cultural and consumerist trends. What used to be fashionable and cool in the previous decades is laughed at today. Those trends and attitudes are not natural. They are shaped and created by a large and powerful PR industry.
If you were born in the 15th century, you'd think that feudalism is the result of a divine order (and human nature) that cannot be changed. You may similarly argue that democracy, the right to vote etc. are not compatible with human nature. Our attitudes and worldviews have changed so many times throughout history that it doesn't make much sense to look for some universal notion of human nature.
It's not true that humans are naturally greedy. No one is born greedy. It's a "virtue" planted in our consciousness by our environment and the conditions we grow up in. Humans rose to the top of the food chain not by greed but cooperation. Only by combining our resources were we able to achieve what we call civilization.
Marx and Engels explained that in any society, the dominant ideology is that of the dominant political and social class. The economically dominant class has the power and wealth to spread the ideology that serves its class interests. They dictate how far we can go with out political thinking. As soon as their ideology is seriously challenged, they'll accuse every critic of extremism. Take the example of Jeremy Corbyn in Britain. His ideas are not communist or even socialist. He's just a genuine social democrat but even that is "extremist" according to the corporate mainstream press.
But what is communism? Well, first we have to understand that a communist society has not been established yet. A communist state is an oxymoron. The main objective of communism is the common ownership of the means of production and the abolishment of private property (of the means of production, not your car, house or smartphone
), social classes, money and the state. As you see there is no communist states and never has been because the state no longer exists in communism. For Marx the communist society is
"an association, in which the free development of each is the condition for the free development of all." It's a society based on an association of free and equal producers. Class antagonisms and the exploitation of man by man will no longer exist.
Communism is not a utopian pipe dream. Marxism is also known as scientific socialism. In order to fight for socialism (an intermediary between capitalism and communism), you'll have to study economy, philosophy, history, technology etc. with a thorough scientific approach. You can't establish socialism just because you're pissed off and feel like starting a revolution. Revolutions happen when a system has hit the wall and when the only solution is its replacement with a more advanced system. For example, industry couldn't have flourished within a system of feudal property relations. Only capitalism was able to liberate the emerging means of prodution of the time and increase their potential and productivity. But capitalism has reached its limits. It has become a large force of destruction, oppression and exploitation. The era of expansion and prosperity is long gone. There are no new markets to conquer except by force.
Will there be a revolution? Will communism ever be achieved? We can't know as we're no prophets and neither was Marx. But it's my conviction that communism is worth fighting for if we want to become a civilization free of war, hunger, slavery, racism, exploitation, religious superstition, illiteracy etc. A civilization in which reason, knowledge, respect and solidarity are what future generations will recognize as human nature.